Nelumbo leaves have been used in traditional medicine to treat bleeding, gastritis, hemorrhoids, and halitosis. However, their mechanisms have not been elucidated.

The present study prepared two Nelumbo leaf extracts (NLEs) using water or 50% ethanol. Inflammatory response was induced with LPS treatment, and expression of pro-inflammatory mediators (inducible nitric oxide synthase, cyclooxygenase-2, tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 and nitric oxide (NO) and prostaglandin E₂ (PGE₂) productions were assessed. To determine the anti-inflammatory mechanism of NLEs, we measured nuclear factor-κB (NF-κB) activity. Major metabolites of NLEs were also analyzed and quantified.

NLEs effectively reduced the expression and productions of pro-inflammatory mediators such as IL-1β, IL-6, TNF-α, PGE₂, and NO. NLEs also reduced NF-κB activity by inhibiting inhibitor of NF-κB phosphorylation. Both extracts contained catechin and quercetin, bioactive compounds of NLEs.

In this study, we showed that NLEs could be used to inhibit NF-κB-mediated inflammatory responses. In addition, our data support the idea that NLEs can ameliorate disease conditions involving chronic inflammation.